In liquid crystal display devices, such as liquid crystal displays (LCD), a retardation film having a controlled optical anisotropy is used for the purpose of optical compensation. As such a retardation film, attention has been focused on a reverse dispersion retardation film capable of, for example, providing a ¼ wavelength retardation in a wide wavelength range of the entire visible light region (400 to 800 nm). Moreover, as such a retardation film, retardation films using a norbornene-based ring-opening polymer have been developed.
For example, Japanese Unexamined Patent Application Publication No. 2003-255102 (Patent Literature 1), Japanese Unexamined Patent Application Publication No. 2004-176051 (Patent Literature 2), and Japanese Unexamined Patent Application Publication No. 2004-323489 (Patent Literature 3) each disclose an optical film made of a specific norbornene-based ring-opening polymer. However, in such conventional optical films made of a norbornene-based ring-opening polymer as described in Patent Literatures 1 and 2, the norbornene-based ring-opening polymer contains an ester group or an imide group which causes the ring-opening polymer to have a low hydrolysis resistance, and the optical film is deteriorated by water content in air. Meanwhile, for conventional optical films made of a norbornene-based ring-opening polymer as described in Patent Literature 3, a very low temperature condition such as −78° C. is required when a raw-material monomer is synthesized. Thus, a dedicated refrigeration equipment is needed to create such a very low temperature state. This brings about a problem of excessive size of the production facilities in considering industrial production.
Moreover, Japanese Unexamined Patent Application Publication No. 2008-52119 (Patent Literature 4) discloses a reverse dispersion retardation film containing a norbornene-based ring-opening polymer obtained from a specific norbornene derivative with an adjusted endo/exo ratio. Further, Japanese Unexamined Patent Application Publication No. 2006-189474 (Patent Literature 5) discloses a retardation film containing a norbornene-based ring-opening polymer obtained by using a norbornene derivative containing spiro rings. Furthermore, Japanese Unexamined Patent Application Publication No. 2005-290048 (Patent Literature 6) and Japanese Unexamined Patent Application Publication No. 2008-7733 (Patent Literature 6) each disclose a norbornene-based ring-opening polymer obtained by using a norbornene derivative containing spiro rings. However, conventional retardation films using a norbornene-based ring-opening polymer as described in Patent Literatures 4 to 7 are not necessarily sufficient from the perspective of achieving both heat resistance and reverse dispersion characteristics.